<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* div 里的所有span 改为红色 */
div span {
color: red;
}
    </style>
</head>
<body>
    <span>span 标签</span>
   <div>
    <span>儿子</span>
    <p>
        <span>孙子</span>
    </p>
   </div>
</body>
</html>